The Zenith El Primero Chrononmaster was one of the first calibres to be fully integrated and designed as an inseparable whole. There was no additional module, but instead a construction built around a column wheel and a central rotor mounted on ball bearings. The movement was then miniaturised and equipped with a date mechanism.

More than 40 years later, the Zenith El Primero Chronomaster is still one of the most precise series-made chronographs, capable of measuring short times to the nearest tenth of a second. It takes an average of nine months to make a single watch in the El Primero Collection. A series of 2,500 operations are performed by 300 expert pairs of hands and 18 different metals are used.